That's also why we dropped MABH way back in the '80s
That's also why we dropped MABH way back in the '80s.
Low DHs below 50' HAT (e.g., 15 ft), where you're below the adjacent taxiway tail heights, and obstacles "fixed by their aeronautical purpose" still make no sense at all. To get below 50' HAT one needs to be sure you're over the TDZ, period. Further, the aircraft are (required) assured to still have safe characteristics in the event of an inadvertent TD in the event of initiation of a low altitude GA.
That's why the AWO HWG long ago agreed that MABH is irrelevant (and JJ LaBlonde, Jacques Rosay, and Gerard Marin were each there for the deliberations), and was not needed. Further, applying any low DH below 50' HAT to any Fail Op A/L was simply an unnecessary distraction at a critical time in flare, ..and that to get below 50' HAT one ought to be Fail-Op or equivalent anyway.
The only few exceptions to this day, were the special cases using a Fail-Op system without a rollout system installed (e.g., some early B747s), which required confirmation of a safe TD and adequate visibility for the initial transition to rollout, ...before committing to a TD,... Or the more recent case of a "Hybrid" Fail-Op system situation, using HUD AIII mode (with reversion rollout capability) to monitor an AP FP autoland as the primary means of control.